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authorCornelia Huck <cohuck@redhat.com>2019-04-08 14:33:22 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-17 08:36:47 +0200
commit208d25a7ae49746d7ff08efcea6cc4e190fa6cfb (patch)
parent97491c03592c3e6586172b40982e581ed7ede3c3 (diff)
virtio: Honour 'may_reduce_num' in vring_create_virtqueue
commit cf94db21905333e610e479688add629397a4b384 upstream. vring_create_virtqueue() allows the caller to specify via the may_reduce_num parameter whether the vring code is allowed to allocate a smaller ring than specified. However, the split ring allocation code tries to allocate a smaller ring on allocation failure regardless of what the caller specified. This may cause trouble for e.g. virtio-pci in legacy mode, which does not support ring resizing. (The packed ring code does not resize in any case.) Let's fix this by bailing out immediately in the split ring code if the requested size cannot be allocated and may_reduce_num has not been specified. While at it, fix a typo in the usage instructions. Fixes: 2a2d1382fe9d ("virtio: Add improved queue allocation API") Cc: stable@vger.kernel.org # v4.6+ Signed-off-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Halil Pasic <pasic@linux.ibm.com> Reviewed-by: Jens Freimann <jfreimann@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2 files changed, 3 insertions, 1 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 8977f40ea441..2f09294c5946 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1040,6 +1040,8 @@ struct virtqueue *vring_create_virtqueue(
if (queue)
+ if (!may_reduce_num)
+ return NULL;
if (!num)
diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index e8d36938f09a..b38c1871b735 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -62,7 +62,7 @@ struct virtqueue;
* Creates a virtqueue and allocates the descriptor ring. If
* may_reduce_num is set, then this may allocate a smaller ring than
- * expected. The caller should query virtqueue_get_ring_size to learn
+ * expected. The caller should query virtqueue_get_vring_size to learn
* the actual size of the ring.
struct virtqueue *vring_create_virtqueue(unsigned int index,